My own opinion is the verse is referring to a lifestyle of sin, the person would not be concerned as to the sin they were committing. Obviously, the verses in 1Peter would refer to people who have shown much change in their lives, and Peter is pointing out other things they need to be rid of
How about this?
In 1 John 3:9, the context is that "
sin is the transgression of the law" (1 John 3:4) so John may not have been referring to what Peter spoke of in his epistle when he spoke of sin?
Of course, the broader definition of "law" as it pertains to "law and gospel" is that it is every moral tenet that can be found in holy scripture.
I will say that I believe that when the Gentile believers that we read about in Acts 15 were converted, that God "
purified their hearts by faith" (Acts 15:9).
If Peter gave practical teaching on what it means to be born again in his epistle, I don't think that he was saying that those who are born again generally bear the attributes of sin that he spoke of in those verses.